Internal combustion engines including diesel engines produce a number of combustion products including particulates, hydrocarbons (“HC”), carbon monoxide (“CO”), oxides of nitrogen (“NOx”), and oxides of sulfur (“SOx”). Aftertreatment systems may be utilized to reduce or eliminate emissions of these and other combustion products. Diesel particulate filters, such as catalyzed soot filters and others, can be used to trap diesel particulate matter and reduce emissions. Diesel particulate filters may undergo soot regeneration or desoot to eliminate trapped diesel particulate matter. There is a need for metrics operable to determine or estimate soot loading of diesel particulate filters or soot filters.